Development and refinement of augmented treatment regimens for pediatric high-risk acute lymphoblastic leukemia

The 5-year survival rate for children and adolescents with acute lymphoblastic leukemia (ALL) is now at least 90%. However, clinical features (age and initial white blood cell count [WBC]), early treatment response, and the presence/absence of specific sentinel genomic lesions can identify subsets of high-risk (HR) ALL patients with a much higher risk of treatment failure. Chemotherapy regimens used to treat HR ALL have been refined over the past 3 decades through randomized clinical trials conducted by the Children's Oncology Group (COG) in North America and the Berlin-Frankfurt-Muenster (BFM) group in Western Europe. Contemporary COG HR ALL treatment regimens were developed from the BFM-76 regimen, with subsequent changes that led to development and refinement of a so-called augmented BFM (ABFM) regimen used today. Although contemporary COG and BFM treatment regimens are not identical, there are many more similarities than differences. With improvements in survival, it has become clear that although the outcome of some patients with HR ALL can be improved by optimizing use of standard cytotoxic chemotherapy agents, this approach has had only limited success for other patient subsets. In contrast, introduction of the tyrosine kinase inhibitor imatinib has led to dramatic outcome improvements for children and adolescents with Philadelphia chromosome-positive ALL. Genomic studies are identifying new sentinel genomic lesions that can serve as potential therapeutic targets, which will likely lead to the testing of novel and/or targeted therapies in more children with HR ALL. Such studies will require increased collaboration between Western European and North American cooperative groups.